Polycarbonate resin is a material which has relatively high heat resistance among polymer materials. However, many types of additives have been used in the polycarbonate resin to meet growing demand for high-function and high-performance materials, thereby reducing the heat resistance of the resin containing such additives.
For example, an internal mold release agent is often added to polycarbonate resin in order to improve the releasability of a resin molded article from a metal mold at the time of melt molding. However, when an effective amount of this internal mold release agent is added, the polycarbonate resin may be colored due to the decomposition of the release agent itself at the time of thermoforming or the induction of the deterioration of the polycarbonate resin by the decomposed product of the release agent.
Patent Document 1 and Patent Document 2 teach that the heat resistance of polycarbonate resin is improved by adding a specific phosphorus-based heat stabilizer to the polycarbonate resin. Although the addition of these heat stabilizers is effective in the improvement of the heat resistance of the polycarbonate, there is a case in which fully satisfactory heat resistance cannot be obtained even by adding a heat stabilizer. When a large amount of the heat stabilizer is used, the mechanical properties and hydrolytic decomposition resistance of the polycarbonate resin may be deteriorated.    (Patent Document 1) JP-A 2001-081302    (Patent Document 2) JP-A 2001-192544